South Korean President Lee Myung-bak and Vietnamese Prime Minister Nguyen Tan Dung called on North Korea today to return to talks, UPI quoted officials as saying. Meeting at the South Korean presidential compound office Cheong Wa Dae, Lee and Dung urged Pyongyang to drop its provocative actions, such as this week's suspected nuclear test, and instead return to the stalled six-party denuclearization talks, the South Korean Yonhap news agency reported. "President Lee and Prime Minister Dung agreed North Korea's recent nuclear test was a serious challenge to the international nuclear non-proliferation regime and a threat to the peace and stability of northeast Asia and the world," a joint news release stated, adding that the leaders called on North Korea to "fully observe the U.N. Security Council resolution (condemning the test) and to immediately return to the six-party talks." Yonhap said Lee and Dung also discussed several other bilateral issues and explored ways to further develop the relationship between their countries, with Lee calling for increased participation of South Korean businesses in Vietnam's development projects.